1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) panel. More particularly, the present invention relates to an optically compensated birefringence (OCB) mode LCD panel.
2. Description of Related Art
To satisfy a quality demand of dynamic images of a liquid crystal display, various fast-response LCD techniques are continuously provided, and one of those is an OCB mode LCD. Because the OCB mode LCD has advantages of wide viewing angle and fast response (less than 5 ms), some techniques about driving OCB mode LCD are developed.
However, one of disadvantages of the OCB mode LCD is that a transition from a splay state to a bend state is necessary for driving the OCB mode LCD, so that the OCB mode LCD requires a high voltage to perform the transition for starting a display driving. However, the relatively high voltage not only increases a cost of the liquid crystal panel, but may also cause damage to the liquid crystal panel. U.S. Pat. No. 6,437,844, filed in 1997, provides a seed concept for an OCB mode LCD. Some regions having high pre-tilt angle serving as the seed is designed in the OCB mode LCD to speed up the transition. However, a higher voltage is needed to transit liquid crystal molecules from a splay state to a bend state, and a higher operation voltage is also required. In addition, etching and developing processes are also required to form the regions having high pre-tilt angle, and therefore this method is complex.
U.S. Pat. No. 6,597,424, filed in 2002, provides a seed structure for an OCB mode LCD. Some protrusions are designed around electrode regions to serve as the seed so as to speed up the transition. However, a higher voltage is needed to transit liquid crystal molecules from a splay state to a bend state, and a higher operation voltage is also required. In addition, the number of the seed formed by the method is limited, and the seed uniformity is not good.
U.S. Pat. No. 6,710,832, filed in 2001, also provides a seed structure for an OCB mode LCD. A non-uniform aligning surface is formed in the LCD such that liquid crystal molecules in some regions of the LCD have higher pre-tilt angle. Hence, a transition seed may be generated during driving the LCD so as to speed up the transition from a splay state to a bend state. However, a higher voltage is needed to transit the liquid crystal molecules from a splay state to a bend state, and the operation voltage is still too large. In addition, the number of the seed formed by the method is not easily controlled, and is easily to have light leakage issue.
U.S. Pat. No. 6,859,246, filed in 2002, provides another seed structure for an OCB mode LCD. A saw-tooth surface composed of slant surface structures is formed in a non-display region of a LCD, such that liquid crystal molecules in the region have higher pre-tilt angle. Hence, a transition seed may be generated during driving the LCD so as to speed up the transition from a splay state to a bend state. However, a higher voltage is needed to transit the liquid crystal molecules from a splay state to a bend state, and the operation voltage is still too large. In addition, etching and developing processes are required, and therefore this method is complex.
U.S. Pat. No. 7,215,397, filed in 2002, provides another seed method for an OCB mode LCD. A secondary alignment is performed on the alignment layers with developing and etching processes, such that variable alignment directions are formed in a single alignment layer. After assembling the LCD, 90° horizontal-twisted regions are formed to serve as an OCB seed to speed up the transition. However, a higher voltage is needed to transit liquid crystal molecules from a splay state to a bend state, and a higher operation voltage is also required. In addition, etching and developing processes are required, and therefore this method is complex.
For the foregoing, many techniques have been developed to speed up the transition from a splay state to a bend state. However, in addition to the transition from a splay state to a bend state is needed, a higher transition voltage is also required to drive the LCD.